Soil runoff ph of 5.1 in flowering

hey guys,

My closet plant is on its 5th week of flowering and appears to be doing fine. However, last feeding (1/4 strength FF trio, the usual, feeding every other watering) the runoff ph came out at 5.1.

Is this something to be concerned about? Should I flush with sledgehammer even though my plant looks fine, or should I just give it regular water for the next few waterings?

I’m just worried because I had my other plant fail due to a ph lockout and I’m wondering if I should just water normally or take the drastic measure of flushing with sledgehammer.

The runoff ppm is 800 btw.

1 Like

A lot of folks flush at the end of week 6 and just ph water the last two weeks. If your that close I’d just ride it out. You can try upping the water ph a bit. If you ph the water at say 7 going in and it still comes out that low you may have lockout already but I’d think you’d know it if you did. If plants healthy this close to harvest just keep an eye on it. I lost all my fan leaves by harvest and still had a good crop.


I was thinking the same thing, since I’m pretty far into flowering with no signs of deficiencies or anything on my plant I think I’ll just save flushing for the last 2 weeks which is coming up soon…but for now I’ll just skip nutes for the next few waterings.

Also, when people talk about flushing for the last 2 weeks, they mean just giving it regular water right? They don’t mean to do a big one day flush?

1 Like

Maybe it’s a malfunctioning meter test it on distilled water to be sure

1 Like

You want to run at least a couple gals thru it ph’d. You want to get all the leftover nutes out before harvest for a better tasting bud. The plant will use up what’s left in it. Then just use ph’d water after that. I’d feed it till the end of 6 weeks.

1 Like

Ah gotcha - thanks so much. It’s coming up soon so hopefully no problems arise before that.

Also @GreenSnek it’s definitely accurate, distilled water is showing up as 6 but just to be sure I’m going to test the runoff of the next watering with my other ph stick that I actually know how to calibrate. Every time I do that the readings are the same on both sticks but I’ll do it to make sure.


You have to use calibration fluid with a predetermined ph to do an accurate test and calibrate the pen. If you think about it what I am about to say makes sense. And, I did not come up with it. A moderator had to explain it to me. Distilled water and RO water is used in growing because of their very low ppm. They also take on the ph of what ever is added to it. These characteristics also prevents you from obtaining an accurate ph of just the distilled water. It has no stuff in it from which to obtain an electric charge which how the meter determines the ph. Once ppm gets to around 100 and above, you can rely on the reading. Therefore, to know if the pen is reading accurately, you need to use an solution with a known ph.
You mentioned you had ph lockout before. Did you figure out why? Or, if you were like me, that is when I bought my first set of ph & ppm pens. What sort of ppm readings were you getting then? I would think your ppm would be higher to generate that low of ph. Or, it is the media you are growing in. Or, the pen is off and needs to be calibrated or replaced.
Make sure you get a good volume of runoff the next time.


Why use nutrients that require you to flush them out in order to get a smooth product? Maybe consider growing organic next time where the end flush of those chemical nutrients aren’t required. Just a thought.


I got ph lockout on my other plant because i was paying too much attention to ppms and ignoring runoff ph. You see, I would measure the runoff ppm with a TDS meter every watering, and a lot of the time the ppms would show up pretty low (around 300-400) so I’d figure that I should feed around 700-800 nutrient ppm for example to bring it up to around 1300. I usually tried to stay around 1000 ppm runoff. well before I knew it my runoff ppm was around 300 with a runoff ph of 4.9. how does this even happen? I flushed it with 7 gallons of tap water (in a 3 gal pot), got my pH up to 5.6 but my runoff ppm was what the tap water is, which is 83.

So I figured ok fine, it’s normal to have washed out all of the nutrients during a flush, at least my pH is up to 5.6, I’ll just feed next watering. So, next watering comes along, I feed 1/4 strength, and boom runoff ph is back to 4.9. This is why I was not able to solve it. The next few waterings I kept flushing with sledgehammer until my plant eventually got so weak it couldn’t even hold itself up on its own and it just fell over.

Despite the discoloration and the falling over, the absolute worst part is how bad it smelled when it was rotting away. Holy crap, that plant smelled worse than a public NYC bathroom on steroids. Anyway it was beyond disappointing because I got rid of all of other plants in my tent a couple months ago to bank it all on this one plant, just to lose it to a ph lockout a few weeks before harvest. You can see why I’m concerned about this low ph now on my healthy plant in my closet. It’s all I got left.

So my lesson learned is this…don’t feed extra nutes just because the ppms are low. Ph lockout is a nightmare because it’s nearly impossible to bring your ph back up once it’s down. That’s why I’m hoping in my next watering for this plant that the ph will go back up to what it was last week at 5.4, which is still low but it’s been holding up pretty well at that number. Just don’t want it to get any lower.

1 Like

Man Heart breaker. I didn’t see what you are using for soil.

1 Like

for real. All that hard work for months just for my first grow to fail because of something tragic.

I grow in FFOF btw. I didn’t start feeding nutes till 3 weeks after the transplant because my runoff ppm came out at 300 and I thought I needed to start feeding.

1 Like

When you mentioned 300 before I was wondering if you used coco or something but that still would not have made sense. Also 300 ppm runoff for FF OF is way less than what I see. I amend my FF OF but I would consistently see PPM over 1000 often high 2K or even 3K. They would bounce around so much that I basically ignored the ppm and paid more attention to ph. If it dropped more than .5 from where I started with a soil slurry test, I would stop nutrients see where it was at and if still high run sum extra ph water through, test, and see where it was next time. I do remember someone having a low ph problem with FF OF. I don’t recall who or how it was resolved.

1 Like

I always had pH issues with ffof


I plan on doing that on my next grow, just paying attention to ph and if it goes low I’ll give regular water more. I learned my lesson from it and I’m excited to start again. I think the reason the ppms got so low so quick is because the plant genetically was just really big, growing really fast and probably eating up more nutrients as a result.

I’m honestly starting to think that Ocean Forest is just a bad soil, I hear more complaints about it than praise, starting to question if I should use Happy Frog instead for my next grow. But then I’d probably have to feed immediately after transplant and I don’t really wanna do that, especially since I’d probably also have to do a flush before switching to flower to get out all the vegetative nutes.

1 Like

I’ve used OF with great success as have many others. Sometimes a less than optimal batch is made that can create issues.

Whether using OF or happy frog or roots Organics etc etc when you pot up (transplant) you are adding all that fresh soil with nutrients so regardless which you use you shouldn’t have to feed them until that starts to become depleted. Just that happy frog might need feeding a little sooner than OF but as I’ve never used HF soil I’m not sure how much quicker you would need to feed versus OF.
I’ve recently started using my own soil mix with the base of Spagnum peat moss (not an endanger resource as I was worried about that issue but concluded that it’s not) compost and aeration at about 1/3 of each for base mix. Then I add dry organic nutrients to that and I have my soil to use. And during grow I’ll top dress dry nutrients as needed.
This depends on how big the plant gets etc bigger plant more food it needs just like more water and light etc etc.
Using organic nutrients it isn’t necessary to flush anything out as the living soil will self regulate things where if there is “residual” nitrogen and the plants needs are reduced for it the plant won’t uptake as much. Nitrogen is used all the way to the end but just not as much used in later flower.
When using chemical nutrients people need to flush that crap out.

1 Like

Yeah, but it doesn’t explain why I would have such outrageously low ph readings along with really low ppms. It makes it very difficult to know when and how much to feed. I used 2 different batches of FFOF and the same thing happened. I also didn’t feed until 3 weeks after transplant and only because my runoff ppm read 300.

What kind of organic nutes would you recommend? I’m assuming FF trio isn’t organic from what I’ve read.

1 Like

There are many options.
Most of my amendments are from Down to Earth and Build a soil.
I primarily use
Worm castings from my worm farm and store bought because I don’t produce enough for my needs.
Oyster shell powder (slow release calcium) and helps buffer PH
Neam seed meal 5-1-2
Alfalfa meal
Kelp meal
Crab meal
Epsom salt
Fulvic acid

Many other options and this list isn’t all that I have or use but will cover the basics.
Here is some reading info to look through…check out the web site shown at top of pics they have some great info.
The whole idea with this approach is not to feed the plant but feed the critters in the living soil and they will in turn process the inputs and get it into a form that the plants can use at their leisure.

I also use things that would otherwise go in the garbage or outside compost pile like egg shells, banana peels and so on that all break down and release their NPK Ca Mg etc etc etc

Hope this helps.
Many roads to the same destination I just want to reduce my footprint as much as possible and grow veggies and medicine to be as healthy for me as possible.

1 Like

Take some OF that you have left in the bag and do a slurry test.

1 Like

I got an update everyone…and I feel kinda stupid about it.

There was something that felt off about my pH stick, so I tested something with my other one and was getting higher readings. I decided to test it using my 7.0 calibration solution, and low and behold my pH stick was reading .4-.5 lower than normal. Although relieved, I’m a bit annoyed because I was probably fine this entire time and could have been feeding nutes. On top of that, I was probably giving my new seedlings water that was slightly above 7.

Is this something I should be worried about?